Method of manufacturing tubing



April 18, 1939. J. KARMAZIN 2,154,942

METHOD OF MANUFACTURING TUBING Filed April 8, 1936 IINVEN'TOI? PatentedApr. 18, 1939 PATENT OFFICE 2,154,942. METHOD, or MANUFACTURING TUBINGJohn Karmazin, Huntington, Ind., assignor to General Motors Corporation,Dayton, Ohio, a corporation of Delaware Application April s, 1936,Serial No. 73,258

1 Claim.

This invention relates to refrigerating apparatus or the like. Moreparticularly, it refers to the manufacture of tubing which may be usedfor refrigerating apparatus and for other purposes.

An object of this invention is to provide tubing, and a method ofmanufacture thereof, in which costs have been reduced materially, and inwhich the seam of the tube may be welded without danger of causing thebonding material to puddle within the tube.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawing, wherein a preferred form of the present. invention is clearlyshown.

In the drawing:

Fig. 1 is a longitudinal cross-section and shows one embodiment of thetube partially manufactured; I

Fig. 2 shows the tube of Fig. 1 in its completed form;

Fig. 3 is a view similar to Fig. 1 and shows a modification of thetubing partially manufactured;

Fig. 4 shows the tubing of Fig. 3 in its completed form;

Fig. 5 shows another modification in its 'completed form;

Fig. 6 is a perspective view of another modification; and

Fig. 7 shows a modified form of strip bonding material.

In practising this invention, a strip of metal is extruded or otherwiseformed with flanged edges. In the modification shown in Figs. 1 and 2,this metal strip I is formed with flanged edges H and I2. This metalstrip is wound so that the edges H and i2 of one loop I3 lock with theadjacent edges of the adjacent loops l4 and [5, this locking arrangementextending continuously throughout the length of the tube at all of theloops of the tube. Bonding material is placed between the interlockededges of the loops. Preferably, this is accomplished by simultaneouslywinding one or more .wires l6, ll of bonding material while the metalstrip lll is being wound. If the metal strip I ll is made of steel, thewires l6 and i1 preferably are of copper or of a copper alloy. After thetube is thus wound, the edges of the loops are rolled, or otherwiseforced together, to flatten out the wires l6 and H and reduce thecorners l8 and I9 substantially to a smooth finish. Thereafter, the tubeis heated in a reducing atmosphere, such as hydrogen, at a sufflclenttemperature to cause the bonding material of the wires l6 and H to flowthroughout the seam and to weld the tube completely. Thereafter the tubeis cooled in the reducing atmosphere. The heating and cooling of thetube preferably isperformed in a furnace through which the tube ispassed.

6 In the modification shown in Figs. 3 and 4, the metal strip 20 isformed with flanges 2|, 22. The strip is wound spirally, and theadjacent 10 edges of one loop are locked with the adjacent edges of theadjacent loops by means of another metal strip 23, in this embodimentbeing U- shaped, which is wound into the flanges of the strip'Zt to lockthe same. Bonding material is placed between the strips and 23, andpreferably this is accomplished by providing one or two wires 2t and ofbonding material, which wires are wound either before or simultaneouslywith. the strip 23. Thereafter, the strip 23 is rolled or 20 otherwiseforced into the tube to flatten out the wires 2% and 25 and the tube isheated in a reducing atmosphereto cause the bonding material to flowthroughout the seams between the strips 20 and 23 and to cause a.certain amount ofpud- 25 dling along the edges 26 which thus tends toform a smooth tube on the outside. In this modification also, the strips20 and 23 may be of steel, and the bonding material may be copper or acopper alloy.

In the modification shown in Fig. 5, the metal strip 30 is formed withflanges 3| and 32, and the strip is spirally wound so that these flangeslock with the adjacent flanges of the adjacent loops to form acontinuous tube. Bonding material may be distributed throughout the tubeeither by rolling a. thin flat stripof bonding material between theadjacent locked flanges or by placing a wire 33 of bonding materialinside of the tube and longitudinally thereof. Thereafter the tube isheated and cooled in a reducing atmosphere to weld the edges together.

In the modification shown in Fig. 6, a strip 40 is formed with flanges4| and 42, and the strip is wound to form a longtiudinal seam 43 alongthe 5 tube. The flanges 4i and 42 are locked together by another strip44, peferably U-shaped, forced into the pockets of the flanges 4| and42, with bonding material in the form of a wire or a strip inside of thestrip 64. The strip 44 is then rolled so completely into the pockets ofthe flanges 4| and 42 to provide a substanti y smooth exterior for thetube, and the tube is t en heated and cooled in a. reducing atmosphereto braze the same.

While I have shown round wires in the various 2 modifications, it is tobe understood that thin flat strips may be used in lieu thereof, thesestrips also being of suitable bonding material such as copper or copperalloy. Such strips may be of a width equal to. the longitudinal portionsof the seams which they occupy, as indicated, in exaggerated thickness,at 50 in Fig. 7. The showing in Fig. l is intended to be representativeof all of the modifications, it being understood that flat strips may beused similarly in the modifications of Figs. 3 to 6 inclusive.

While the form of embodiment of the invention as herein disclomd,constitutes a preferred form,

it is to be understood that otherforms might be adopted, all comingwithin mescope oft heclaim which follows:

What is claimed is as follows:

The method of manufacturing tubing having substantially smooth inner andouter surfaces which comprises spirally winding a metal strip havingedges of reduced thickness provided with narrow grooves, locking theedges of one loop thus formed with adiiacent edges of adjacent loopswith a U-shaped strip of metal inserted in said grooves, insertingbonding material between said strips,- and heating said tube to bondsaid edges.

- JOHN KARMAZIN.

